1. Field of the Invention
The invention relates to a bit, in particular a round shank bit, having a bit head and a bit shank, a mounting sleeve being held in the region of the bit shank; and having a support element that comprises a guidance region.
2. Description of the Prior Art
A bit of this kind is known from DE 37 01 905 C1. The mounting sleeve is embodied here as a clamping sleeve that is constituted from a resilient material, for example sheet steel. It comprises a longitudinal slot that is delimited by sleeve edges. The mounting sleeve diameter can be varied by means of the longitudinal slot, in which context the sleeve edges are to be moved toward one another (smaller diameter) or spaced farther apart from one another (larger sleeve diameter). Different clamping states can be achieved in this fashion. The support element, embodied as a wear protection disk, is pulled onto the mounting sleeve. This support element has a circular cross section and is penetrated by a bore. The bore is dimensioned such that the mounting sleeve is held, as compared with its slackened state, in a preloaded state having a decreased outside diameter. The outside diameter thereby generated is selected so that the clamping sleeve can be slid with little or no energy expenditure into a bit receptacle of a bit holder. The sliding-in motion is limited by means of the support element. Upon further insertion of the bit shank into the bore, the support element is moved into a region of the bit shank not surrounded by the clamping sleeve. The mounting sleeve then springs open radially and braces itself in the bore of the bit holder. The round shank bit is thereby held in axially captive fashion, but freely rotatably in a circumferential direction. For deinstallation of the bit, it is driven out of the bit receptacle by means of a mandrel acting on the back side of the bit shank.
There are application instances in which the bit can no longer be used for certain milling purposes when it is partly worn away. It is then dismantled, and new unworn bits are installed. The partly worn bits are, however, then still suitable for coarse processing tasks. Because the support element has already been slid away from the mounting sleeve, however, installation then becomes more complicated. Separate clamping tools are used, with which the clamping sleeve can be preloaded in forceps fashion. The bit can then be inserted into the bit receptacle without energy expenditure. The clamping tool is taken off while the bit is in a partly inserted state, and the bit is then driven completely into the bit receptacle with a hammer.
DE 10 2005 042 663 A1 discloses a further bit. A wear protection disk is likewise used here as a support element which holds the mounting sleeve in a preloaded state. The support element can be shifted toward the bit head until the mounting sleeve springs back radially. The support element then engages with protrusions into receptacles of the mounting sleeve, resulting in a non-rotatable bearing point between the mounting sleeve and the support element. Non-rotatable bearing points of this kind have proven to be disadvantageous, since they cause intensified and inhomogeneous wear.
EP 1 427 913 B1 discloses a bit in which a support element can once again be slid off from a mounting sleeve. The support element comes to rest between the bit head and the free end of the mounting sleeve. The support element has, on its side facing toward the mounting sleeve, a peripheral protrusion. The clamping sleeve can become wedged in place on this extension as the bit is driven out, with the result that the clamping sleeve becomes unintentionally spread. Deinstallation then becomes difficult and laborious.